Method of obtaining a concentrated so, solution



APPLICATION FILED JULY 3v [917.

Patented J unc 1, 1920.

LQEQLWMQ SULPHUR BURNER 0R PYAITE ROASTER- sreolve' .50

SOLUTION.

tion filed September 1, 1916,

118,156, of which the present application is has nIELs c. cnnisrn'nsnn', or SALT 'BARLOW, or nanana, or srarn or "omen.

METHOD OF OBTAINING A CDNCENTRATED S02 SOLUTION Grig'inal application filed ESeptember 1, 1916, Serial Ho. llama; Divided and 3, 191?. Serial No. 178,442.

To all whom it may concern 4 Be it known that I, NIELS C. Crinrsrnlvsnn, a citizenof the United States, residingat Salt Lake City, in the county of Salt Lake and State of Utah, have invented certain new and useful Improvements in Methods of Obtaining a Concentrated SO, Solution; and I do hereby declare that the following is a full, clear, and exact description of the same, referencebeing had to the accompanying drawings, forming part of this specification. I

This invention relates to a method oiobtaining a solution of sulfur dioxid, S0,, in an S0 absorbent menstruum, such as water. The primary object in view is the provision of an improved method of absorbing SO, gas in a suitable absorbent menstruurmwhereby a concentrated SO solution is obtained.

The concentrated SO, solution obtained by practising the method of this invention is especially useful in connection with the lixiviation of copper ores for the recovery of copper, for example, in the lixiviation methoddisclosed in my co-pendin applicaerial No.

a division. It will be understood, however, that the concentrated S0 solution obtained. by this invention is not necessarily limited in its useful application to the art of lixiviating copper, but may be applied to other useful applications as well.

The accompanying drawing illustrates diagrammatically an apparatus employed in carrying out the present improved method, and the several steps constituting the same. Before setting forth in detail the method, the principlesunderlying the same and on which successful results are dependent, will first be briefly set forth. It is Well u.nder' stood that, in order to secure an etficient absorptionof SO, gas, absorptirm apparatus of suilicient capacity must be used and there must also be suflicient volume of the absorbent menstruum. While these elements necessary for eflicient absorption present no serious dilliculties, the maximum strength of the solution finally obtained, or the degree of concentration Which/may be secured an absorption apparatus is, however, not determined to any great extent by the eiliciency of the apparatus. On. the otherhand the Specification of Letters Eatent.

, rateiaeusnne 1, race.

strength or degree or" concentration of the b0, solution depends almost entirely upon the percentage of SO, in the gas supplied to only 18% S0,; 2'. e, the richest gases from a sulfur burner, a solution'carrying a little this application filed July over 276 80, might be obtained, while, if a 6% SO, gas be used, (2., the gases from a roasting furnace, the solution obtained would contain only about .770 S9,.

From the above it is conclusive that the process of obtaining a concentrated solution of SO, cannot be made a success by utilizing only a dilute roaster gas, as has been heretofore attempted. Relatively. strong solutions necessarily cannot besecured from relatively dilute gases in any absorption apparatus. In accordance with the present invention, it has been ascertained that, in order to secure a strong and concentrated solution-of S0,, dilute gases must first be absorbed in an absorption apparatus to fornia weak solution, and this weak solution must then be enriched by further ab-, sorption of SO, in another absorber or another section of the absorption apparatus, to which richer gases are supplied. The

above is one of the most important elements I of the process and results in obtaining a highly concentrated SO, solution, suitablefor .ljxiviation mrposes and for many other uspl'ul applications.

As shown in the accoi'npal'iying drawings, the absorbent menstruum, usually water, is passed tl'irougli the first section of the ab sorption apparatus, indicated by the rotten ence character 1, and absorbs the S0 gas escaping from the second. section of the absorption apparatus, thereby utilizing all the residual gas from the second section of the absorption amiaratus. To this second sontion 2 the relatively weak solution passes and absorbs SO gases supplied from a roaster or'sulfur burner 3 Also supplied to the second section of the absorption apparatus are S0 gases escaping from the third section of the apparatus, indicated in the drawing by the reference character 41-. From the second section; the solution of Water and S0 is next passed. through the third section, and saturated to the desired extent. Very'strong, or relatively pure SO gases are supplied to the third section of the apparatus from a boiler or precipitate roaster such as is mentioned in my said co-pending application.

In practising the foregoing method, astrong or highly concentrated solution of- SU in the absorbent menstruum is secured. Furthermore, 'all escape of. S0 gases involving loss of S0 is cut ofi,-as residual gases from successive sections or the apparatus or successive absorbers are utilized to saturate the solution passing through preceding sections of the ap 'iaratus. It will be noted further that the solution is subjected to successive absorptions of S0 in the order in which the S0 gases increase in SO content.

' solution or fresh Waterin the first section of the absorption apparatus is caused to absorb S0 from gases containing a comparatively small quantity of S0 and thus all the S0 is utilized; Whereas in the third section of the apparatus the solution is partially saturated with SO and is brought nto absorbing relation with practically pure SO gases.

The unsaturated sections of the absorption apparatus might be used, the number of sections being deterrhincd by the strength of the solution desired and the use to which the concentrated solution is put. -ln most cases, however, it will be found that three sections are amply suilicient for obtaining a highly concentrated solution oi? S0 in the absorbent menstru um. i

\Vhat is claimed is:

1. In a process-in which a concentrated SO solution is deprived of part of its S0 and is later caused to absorb the S0 so doprived, the step of replacing the losses oi $0 to the system consisting in: causing the weakened solution to first absorb the relatively weak replacement S0 and thou causing the absorption by the thereby strengthened solution of the relatively strong S0 gas previously taken from the solution.

2. In adeviee for obtaining a concentrated SO.) solution, a source of supply of relatively pure So 'gas, a separate source of supply of relatively weak S0 gas, a safety'absorber, a Weak absorber, a strong absorber, means for passing an SO absorbent menstruum through said absorbers in the order mentioned, means for conveying the relatively pure S0 gas to the strong absorber, means for conveying relatively Weak S0 gas and the residual gas. from the strong absorber to the weak absorber, and means for passing the residual gas from the Weak absorber to the safety absorber.

/ .NIELS C. CHRISTENSEN. 

